In communications networks where multiplexing schemes transfer pulse signals from one node to another, usually ground loops become a source of noise. Noise results especially when large distances separate multiple ground points and during employment of low-level analog circuits. It becomes necessary to provide some form of discrimination or isolation against ground path noise and direct current offset voltages.
Grounding of nodes in multinode systems occur at different points resulting in potential differences between grounds; e.g., chassis ground and signal ground. Grounding components in vehicles necessitate this grounding approach. This usually causes unwanted noise voltages in the network. The magnitude of signal levels compared to noise voltages in the network provides a signal-to-noise ratio. If the signal-to-noise ratio affects network operations, then effort to improve the ratio must take place.
Past noise reduction remedies included two basic approaches: 1) avoid the ground loops by removing one of the type grounds and converting the system to a single-point ground network. (This provides an impractical remedy since DC currents cause very large voltage drops); 2) eliminate or minimize the effects of multiple grounds by isolating the two or more circuits. Isolation can be achieved by using: 1) transformers, 2) common-mode chokes, 3) optical couplers and 4) balanced circuitry.
Such techniques yield favorable results, but these techniques require large numbers of isolating components. Such components are costly and may introduce other adverse effects entirely unanticipated.
In an effort to minimize isolation problems in multinode networks, a search took place to find other means of isolating ground loops in multinode networks. That search resulted in the present invention which substantially eliminates noise potentials between grounds in multinode networks.